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UNIDENTIFIED MALE (voice-over): This is CNN breaking news.

PAULA NEWTON, CNN ANCHOR (voice-over): Hello, I'm Paula Newton at CNN Center. We are following breaking news out of Thailand this hour. A high-risk operation to rescue that youth football team is now underway. They remain trapped in that flooded cave. Now just minutes ago the local governor called it D-Day.

In the meantime, media and non-essential personnel have been moved from the camp near that cave entrance. For the latest, CNN's David McKenzie is on the ground in Northern Thailand.

David, an excruciating decision for everyone and apparently one that was shared with the parents.

DAVID MCKENZIE, CNN CORRESPONDENT: Definitely shared and in a way it was the parents who gave the final green light here. So much is at stake for their families, this community, Thailand and, of course, for everyone following this extraordinary story around the world.

The news is this, that this is the D-Day, behind me in the mountains you can see that save system which has captured everyone's attention. Those 12 boys and their coach, ages 11 to 16, will be doing the excruciating extraction with these specialized divers; 13 international divers made their way into the cave about an hour ago, when this operation began.

We shouldn't expect a resolution any time soon. The governor saying that the first boy, if successful, will get out much later today, even possibly in the evening Thailand time. They have prepped. They have drilled. They have the medical teams on standby. If anyone can pull it off, it's them. But this is a rescue attempt like no other -- Paula.

NEWTON: David, do you have a good sense of how many hours -- do they have a good sense of how many hours it will take for each one?

Are we talking about five hours?

Six hours?

Do they have any estimate on that?

MCKENZIE: You know, any amount of hours or time in these cramped caverns will feel like a lifetime for both the divers and those boys; as I said, so much is at stake. We don't know exactly.

There have been various estimates of how long it takes from the chamber three, which is sort of halfway through the cave system, in which they have managed to take out much of the water.

And the water and the oxygen levels, those are the big factors here. It's lightly raining on my head right now in Northern Thailand. The monsoon is due to start soon. And so they feel this is the best hope they have of getting these boys out.

NEWTON: In fact, they got lucky in the weather in the sense they haven't had torrential rains. They were able -- I was impressed with how much water they were able to take out.

Do they feel that will give the boys some breathing room, that, what looked like an absolutely impossible dive, save for experts a few days ago, will now make it just slightly easier for those boys to be able to endure this?

MCKENZIE: Yes, I think it will be a little bit, if not easier, possible. They have managed to, 24 hours a day, pump that water out from several pumps. There's -- you know, it is a military operation on that mountainside behind me.

That has allowed them to at least -- the section of the cave, from the command control center in the chamber three towards the entrance, the boys will be able to walk or crawl out.

From there in, there is still a very treacherous dive that only the most experienced cave divers on the planet are willing to entertain. And now they are taking these boys out.

What they will do, Paula, is have a full-face mask, most likely a 5- mil wetsuit to keep them warm and also keep them safe from bashing up against the tight spaces.

Two divers most likely through most of that section will be guiding those boys through the zero visibility water. They have been taking up glow sticks that they can snap and run for 80 hours.

That won't help the visibility but there will be a sense perhaps to help the boys' calmness that ordeal. The biggest issue is that they mustn't panic. That's partly why they will take one boy out at a time.

If they can keep calm, if they can drag them through by any means necessary, rise through to that chamber to where they can walk out, that will be the moment that we know if it's possible. The first child that --

[00:05:00] MCKENZIE: -- gets through is the key. Then they will know they can do it. Then it's by no means guaranteed that all can get out. They have medics on standby of course. Ambulances on the scene. They will rush them to the local hospitals.

But this could be many hours, even days to know who gets out and if those families will have a welcome reunion.

NEWTON: All the details you are giving there, David, so important and yet so unnerving in terms of what everyone is facing. In the coming hours you will be there to update us on all of it. Appreciate it, David. Please stand by as we talk more about weather.

The approach of those monsoon rains that David was just talking about are factors weighing heavily on this rescue effort.

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NEWTON: Now for more on the breaking news situation in Thailand, joining me now on the line is cave explorer, Emily Davis. She was rescued from a cave after being trapped for 91 hours.

I mean, 91 hours must have felt like a lifetime.

What are you hoping for the rescuers and for the boys at this time?

EMILY DAVIS, CAVE EXPLORER: I think they just need to keep up the positive attitude they have had. I have heard about the letters they wrote to their families, looking for Kentucky Fried Chicken and various other things when they get out.

If that attitude is kept up, if the positive attitude is continued by the families, the boys, the rescuers, I think it will be a far better chance of a positive outcome.

NEWTON: You are talking about a far better chance.

When you were in this situation yourself and you look at this situation, what are the feelings that you would like to express to them or that you feel that would make the families feel better about this?

I think one of the things people are thinking about is we were all so euphoric when we found out they were alive. Yet they are still in so much danger.

DAVIS: The issue is that finding them alive meant that there needed to be a rescue. It didn't mean that the rescue was over. The rescue just began when they were found alive.

And now the technical aspects of the rescue, the difficult parts, the way that they are going to get them through the tight spots underwater, all of those things have to be figured out by people who have been working on cave rescue for many, many years. There is an international community of people who study cave rescue,

who work on cave rescue. You have got some amazing British divers there, who really know what they are doing. And they have to plan this down to the last possible --

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DAVIS: -- iota of technique, of how they are going to proceed.

And the problem is that the general public thinks that you just go in a cave and you come out. We are talking two and a half miles of highly technical, skilled cave exploring, because of the water, because they are wading in water, because you can become hypothermic even in 70-degree water.

NEWTON: We are showing pictures, Emily, as you are speaking of conditions that look tough. And it's really nothing. These are people walking through, trying to make the preparations. Imagine trying to submerge yourself in the water.

Emily, we can't make too fine a point of the fact that these 13 rescuers are risking their own lives to do this.

DAVIS: Yes, yes. One of the things we have to do is, they have to plan so well that there is little chance of anything going wrong. That's why they are taking so much time doing the planning.

But they are pushed hard because of the monsoon weather coming in and because of the lowered oxygen levels. So they are just having to do this planning very carefully but very quickly at this point.

NEWTON: Emily, having been in the situation before, mentally you are one of the few people that can really put yourself in their shoes.

What worries you most right now?

DAVIS: It's hard to compare. I was already caving for 20 years when I had the accident I did. And I was never actually trapped. It just took, because of the amount of time it takes to do technical caving and cave rescue, it took those four and a half days to get me out.

But there was never a situation the way the boys are. I think that the main thing that I have said before and I will say again, is positive attitude, a sense of humor and just drumming up the most courage they have is what they need.

And I think that the rescuers will be able to lead them into that because one of the things that most of these rescuers have studied is psychological aspects of rescue.

So keeping the kids' positive attitude up -- one of your other guests mentioned that getting the first one of the boys out and out in good shape would benefit all of the rest of them for the rest of the rescue.

NEWTON: Yes, you can imagine that, if they learn of that, that it will give them impetus and hope that I'm going to make it out as well. I can only imagine how psychologically that would be helpful.

DAVIS: I'm guessing they might try to take one of the strongest kids out first, the one who is doing the best. And then that whole psychological impetus of knowing that somebody has made it out, they can do it, too.

NEWTON: Emily, thank you so much for sharing your experience with us as we watch, riveted, really, we are all riveted by this extraordinary rescue attempt. Emily, thank you again. We will have much more on the breaking news from Thailand right after this.

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NEWTON: Back to our breaking news story at this hour. A high-risk operation is underway to pull a youth football team out of the flooded cave where they are trapped.

Just minutes ago the local governor called it D-Day. Media and non- essential personnel have been moved from the camp near that cave entrance. For the latest, we go to CNN's David McKenzie, who is following all the developments.

David, you rightly pointed out it was the parents who had to give their blessings to this.

What were some of the risks they were warned about as we now know this operation, even if they didn't want to go through with it today, that they had to, that they had no choice. This was really the best opportunity to save these boys.

MCKENZIE: That's right. If people have just joined us, this is the moment that we have been waiting for and the parents have been waiting for, for days. The young boys, 12 of them, plus their coach, hunkered down for 16 days in the cave system in the mountain behind me.

They will start bringing them out now but it could take hours and it will be treacherous. They would have been warned, Paula, about what those boys will go through. I think the authorities here have been honest about the risks. They have been updating the press and the parents, of course, regularly.

Generally, as you would expect, they will tell the parents and the community everything first before they come to us, just to clear it with them and get them out.

Two new images I want to share with you today from the Thai Royal Navy. These specialist divers kitting up, getting ready for the journey up the Hill, through to the forest to the cave entrance and then deep into the bowels of the Earth, where the operation will take place; 13 international divers, Paula, will be leading the operation alongside their counterparts of the Thai Navy, who are in charge of the rescue.

And the stakes are high. And obviously, the feeling is higher still because of the tragic death of the 38-year-old former Thai Navy SEAL diver. He was -- died a few days ago, taking oxygen to those boys, died on the way back.

That really led a whole other level of seriousness to this rescue operation. I think we have some sound from him, a video that he took of himself before he left to come to the scene.

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MCKENZIE: You know, this Thai Navy diver, he was really someone to come here, give his life selflessly, Paula, for this operation, to rescue those kids. And now his counterparts will be going and making the treacherous journey to get them out.

NEWTON: David, as you were speaking, we were showing that video. It shows these young, healthy boys playing football, soccer.

I have to wonder, what have authorities said about the youth?

I know we have spoken so much about the fact that they need to stay calm and they need not to panic. Yet we have to believe that their youth will actually work in their favor as well, right?

I mean, help them pull them through in terms of having that optimism and really that resilience.

MCKENZIE: Definitely that resilience. And the key issue is that they don't panic, Paula.

The other issue, which is more just a technical issue, is they are small. These kids are young kids and teenagers, 11 to 16. They are able to squeeze through these small spaces, possibly easier than the grown men that are going the rescue them. That is actually quite an important factor.

So getting them out will be hugely challenging. To describe it to our viewers, they will be using a guideline, possibly glow sticks. But still, the visibility will be zero. They have managed to shorten the length of space that they will have to dive, Paula.

But it will still be very difficult. You can imagine at times a diver on either side of these boys pushing them through. As your guest said last hour, though the water here is relatively warm, because it could take even hours if things go wrong to get them through that section of diving, you know, hypothermia is a risk.

They are wearing 5-mil thick wetsuits to both protect themselves from the rocks above and below and --

MCKENZIE: -- also just to keep them warm.

NEWTON: David, we appreciate all those crucial details as we wait and watch and of course hope it will still be many hours. We will bring you the updates as soon as we have them. David, thank you again.

But a lot of what David was talking about there, he is trying to give you the details of what it's like. We have been talking about the adversity, right, rain, flooding and the low oxygen levels are key factors affecting the rescue operations. Look now at CNN's Tom Foreman, who is helping us take a look at the conditions inside the cave.

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TOM FOREMAN, CNN CORRESPONDENT: The only way air moves in and out of most caves is by a change of temperature on the ground above. And that would be true here as well.

However, when you go two and a half miles in and more than a half-mile down, there will be virtually no effect from that. For practical purposes, these boys and their coach are in a sealed chamber, where the air is running low, if not running out.

How low?

They should be getting 21 percent oxygen in every breath. Right now they are repeatedly down to about 15 percent. That means there is decreased stability to work strenuously. They have impaired coordination. You might not think very clearly and, in some cases, they may have decreased vision in low light.

It is not necessarily permanent and they are bringing oxygen tanks in so that may help. But it is worrisome.

In the meantime, outside, they are trying to pump all this water away and they're making some progress. Currently they're getting more than 400,000 gallons out per hour. That's two-thirds of an Olympic-size swimming pool. The idea is maybe you can open some narrow gap and get some of these kids out quickly.

But what we are seeing from inside this cave, from the maps we see, is that there are still several areas that are very flooded, where the kids would absolutely have to go through in scuba gear, for 20 minutes, 30 minutes, an hour, more. We just don't know. It's a big ask and it is not getting any better.

Think about it: everything they have been pumping out now has been water that showed since the kids went into the cave. They've had actually a little lull here without much rain. But much more rain is coming and there's no indication that these pumps can keep up with it.

For all of that though, the single biggest issue here continues to be the topography of the cave. Yes, there are strong currents and it's cold and they can't see. But there are areas here that are so small only one person at a time can go through. The divers are even taking their tanks off and pulling them behind them. That is why it's so hard to get supplies in and out. That's why you can't really even have a serious discussion about trying to lay a pipe over all this distance to take air in. And imagine trying to pull a frightened, exhausted teenager through that underwater.

It's a 6-hour journey from the outside in for even experienced divers. Engineers are saying basically that should be used as nothing but a supply line right now and they should start pounding in from above with some kind of small supply opening to drop food and fresh water through and to pump air in and simply keep these boys alive until they can figure out how to free them.

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NEWTON: Sobering details from Tom Foreman. Stay with us. We will have much more on this breaking news story when we come back.

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NEWTON: We will bring you up to date on the breaking news out of Thailand. The high-risk operation is underway --

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NEWTON: -- to free a youth football team trapped in a flooded cave. Prayers of a nation and many around the world rest on a team of Thai and international divers.

The local governor said earlier that divers have now entered the cave. He called it D-Day and said rescuers were at, in his words, "peak readiness."

But he also indicated, of course, that the rescue was risky and would take many hours, perhaps each days. And we will continue to bring you up to date on that story in the hours ahead.

We are now though following another story in the region. Record rainfall is devastating entire communities in Southwest Japan. At least 48 people have died and dozens are injured by flooding and landslides and by collapsed homes. The government is urging millions to evacuate with more severe weather on way.

We want to get the latest now from Kaori Enjoji. She joins me now live from Tokyo.

It has been a concerning situation as you see those pictures and the authorities that have been caught off guard, especially as the death toll has risen. I think we are trying to get a sense of whether or not the worst is over at this point.

KAORI ENJOJI, JOURNALIST: Paula, they are still calling this a disaster of historic proportions. I am afraid to say they don't feel that the worst is over. The death toll still continues to mount. The Japanese government saying 48 people have been confirmed dead. Another 28 reported with cardiac arrest. That takes the total to 76.

And we know that dozens are still missing and tens of thousands of people have been evacuated from their homes. They are calling this a disaster of historic proportions because the torrential rain has been going on for three, two and a half, three days.

In some cities they got more rain in one day, in 24 hours, than they would in an average month. And there have been fresh warnings issued in various parts of the country as early as this morning. The worst does not seem to be over.

With the amount of rain that some of these regions have gotten, they are warning of landslides and overflowing rivers.

Some historic cities like Kyoto, their rivers going through it that are gushing with rainwater. These are pictures that you would never really see before.

Train services have been stopped, not only to the southwestern part of Japan. What's critical about this disaster is that it's affecting a large area of Japan. Central Japan also seems to be heavily impacted, very populous areas like Hiroshima as well.

So, Paula, it does not seem that the worst is over from the torrential rains here in Japan.

NEWTON: Interesting to see all of those photos as well. You can see why they continue to ask for more evacuations. We really appreciate your update.

In the meantime, we want to thank you all of you for joining us here at NEWSROOM. I'm Paula Newton. I will have the headlines right after a break.